The present invention generally pertains to electrical controllers and is specifically directed to temperature responsive controllers for use in controlling the circulation of water in solar energy conversion systems of the type wherein water is circulated between a solar energy collector and a water storage sump to transfer heat energy to the sump.
A prior art solar energy conversion system is shown in FIG. 1, Energy from the sun is collected in a solar collector system 20, and heats water contained therein. Water is circulated by a pump 21 between the collector system 20 and a water storage sump 22 through pipes 23 and 24 to heat the water in the sump 22. A pump motor 25 is controlled by an electrical controller 26. Connected to the controller 26 are a sensor 27 for sensing the temperature of the collector water and a sensor 28 for sensing the temperature of the sump water. Signals representative of these temperatures are provided on lines 29 and 30 to the controller 26. In response to a comparison of the sensed temperatures of the collector water and sump water, the controller controls the energization of the motor 25 as represented figuratively by line 31 in FIG. 1.
Whenever it is sensed that the collector water temperature is greater than the sump water temperature by a predetermined difference, the controller connects the pump motor with an electrical power source to cause the pump to circulate water between the collector and the sump. When the predetermined difference no longer is sensed, the pump motor is disconnected from the power source. Prior art controllers contain relays for connecting the pump motor (typically an induction motor) to an AC power source.